Supplemental Financial Information (Narrative) (Details) (USD $)	6 Months Ended
	May 31, 2012
Condensed Financial Statements, Captions [Line Items]
Guarantee by subsidiaries	$ 75,000,000
5.95% Senior Notes Due 2013 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	5.95%
5.50% Senior Notes Due 2014 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	5.50%
5.60% Senior Notes Due 2015 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	5.60%
6.50% Senior Notes Due 2016 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	6.50%
12.25% Senior Notes Due 2017 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	12.25%
6.95% Senior Notes Due 2018 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	6.95%
2.00% Convertible Senior Notes Due 2020 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	2.00%
2.75% Convertible Senior Notes Due 2020 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	2.75%
3.25% Convertible Senior Notes Due 2021 [Member]
Condensed Financial Statements, Captions [Line Items]
Interest rate	3.25%
Letter Of Credit Agreement 3 [Member]
Condensed Financial Statements, Captions [Line Items]
Line of credit facility current borrowing capacity	200,000,000
Letter of Credit Agreement 1 [Member]
Condensed Financial Statements, Captions [Line Items]
Line of credit facility current borrowing capacity	$ 150,000,000